JP2016140887A - Low pressure casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low pressure casting apparatus capable of surely obtaining prescribed pressure when gas such as compressed air is supplied to the inside of a holding furnace.SOLUTION: A low pressure casting apparatus 1 introduces gas into a holding furnace 3 for heating a molten metal M and pressurizes a liquid level of the molten metal M so as to fill the molten metal M in a cavity 6 via guide means 10. The holding furnace 3 includes a casing 11; a furnace body 12 stored in the casing 11; and a refractory layer 13 which is disposed between the casing 11 and the furnace body 12 and has a pore structure. The low pressure casting apparatus 1 further includes first gas supply means 14 for supplying gas to pressurize the molten metal M to the furnace body 12, and second gas supply means 19 for supplying gas to the refractory layer 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a low pressure casting apparatus.

  2. Description of the Related Art Conventionally, as a low-pressure casting apparatus used for low-pressure casting, a low-pressure casting apparatus that includes a casting mold and a holding furnace that is provided below the casting mold and holds the molten metal warm is known (for example, Patent Documents). 1).

  The casting mold includes a cavity having a shape along the outer shape of the cast product and a gate connected to the cavity, and the gate is connected to the stalk via a gate sleeve. The lower part of the stalk is inserted into a molten metal whose temperature is kept in a holding furnace.

  According to the casting mold, by supplying a relatively low pressure gas such as compressed air into the holding furnace and pressurizing the surface of the molten metal, the molten metal is put into the cavity via the stalk, the gate sleeve and the gate. Press fit. And a casting can be obtained by cooling and solidifying the molten metal in a cavity, maintaining the pressurization state by gas, such as compressed air.

  In the casting mold, the holding furnace includes a metal casing, a furnace main body housed in the metal casing, and a refractory layer disposed between the metal casing and the furnace main body. The refractory layer is made of a porous body having a pore structure, for example, and acts as a heat insulating material to prevent the heat of the molten metal from being released to the outside, while maintaining the molten metal at a predetermined temperature. can do.

Japanese Utility Model Publication No. 1-89851

  However, in the conventional low-pressure casting apparatus, when the gas such as the compressed air is supplied into the holding furnace and the molten metal is press-fitted into the cavity, or the pressurized state by the gas such as the compressed air is maintained, When the molten metal in the cavity is cooled and solidified, there is a disadvantage that a predetermined pressure may not be obtained.

  An object of the present invention is to provide a low-pressure casting apparatus capable of solving such inconvenience and reliably obtaining a predetermined pressure when a gas such as the compressed air is supplied into the holding furnace.

  In the conventional low pressure casting apparatus, when a gas such as the compressed air is supplied into the holding furnace, a predetermined pressure may not be obtained. It is possible that When the crack occurs in the furnace body, a part of gas such as compressed air supplied into the holding furnace leaks from the crack to the refractory layer and fills the pore structure of the refractory layer. You will not be able to get.

  Therefore, in order to achieve the above object, the low-pressure casting apparatus of the present invention includes a casting mold having a cavity having a shape along the outer shape of the cast product, and a molten metal provided below the casting mold. A holding furnace for holding the temperature; and guide means for guiding the molten metal in the holding furnace to the cavity; and introducing the gas into the holding furnace to pressurize the liquid level of the molten metal, thereby guiding the molten metal to the guide In the low-pressure casting apparatus for filling the cavity through the means, the holding furnace is disposed between the metal casing, the furnace main body accommodated in the metal casing, and the metal casing and the furnace main body. A first gas supply means for supplying a gas for pressurizing the molten metal to the furnace body, and a second gas supply means for supplying a gas to the fireproof layer. It is characterized by providing.

  In the low-pressure casting apparatus of the present invention, since the gas supplied from the second gas supply means is filled in the pore structure of the refractory layer, the gas is supplied from the first gas supply means even when the furnace body is cracked. The gas that is used acts only to pressurize the melt in the furnace body. Therefore, according to the low-pressure casting apparatus of the present invention, when the molten metal is pressurized with the gas supplied from the first gas supply means, a predetermined pressure can be reliably obtained.

  In the low-pressure casting apparatus according to the present invention, it is preferable that a plurality of the second gas supply means are provided, and thereby filling when the gas is filled into the pore structure of the refractory layer from the plurality of second gas supply means. The speed can be increased, the casting cycle time can be shortened, and the entire refractory layer can be filled with gas evenly.

  In the low-pressure casting apparatus of the present invention, the first gas supply unit and the second gas supply unit may each include an independent gas supply source or a common gas supply source. .

  By the way, in the casting apparatus of the present invention, each of the gas supply means includes a gas supply path for supplying a gas and an electromagnetic valve for opening and closing the gas supply path, and further controls the opening and closing of the electromagnetic valve. Can be provided.

  When the applied voltage is increased, the degree of opening of the solenoid valve increases and the amount of gas supplied by the gas supply means increases. To facilitate the management of the gas supply amount, the applied voltage is gradually reduced. It is desirable that the gas supply amount be proportional to the applied voltage when the valve is opened after being increased.

  However, depending on the characteristics of the solenoid valve, when the applied voltage is gradually increased to open the solenoid valve, the gas does not change with respect to the change in the applied voltage until the applied voltage reaches the first predetermined value. The change in supply amount is small. Further, the gas supply amount is proportional to the applied voltage from when the applied voltage exceeds the first predetermined value until it reaches the second predetermined value. However, after the voltage exceeds the second predetermined value, the third predetermined value is reached. Until the opening degree is fully opened, the change in the gas supply amount becomes small with respect to the change in the applied voltage. That is, in the solenoid valve, the gas supply amount cannot be made proportional to the applied voltage only by gradually increasing the applied voltage.

  Therefore, it is conceivable to correct the applied voltage so that the gas supply amount is proportional to the applied voltage.

  That is, in the casting apparatus of the present invention, the first gas supply means includes a first gas supply path that supplies gas to the furnace body, and a first electromagnetic valve that opens and closes the first gas supply path. And the second gas supply means includes a second gas supply path for supplying gas to the refractory layer, and a second electromagnetic valve for opening and closing the second gas supply path, and When the solenoid valve is opened by gradually increasing the voltage applied to the solenoid valve, a correction value is added to the applied voltage so that the amount of gas supplied by each gas supply means is proportional to the applied voltage. It is preferable to provide a control device for controlling the opening of each of the electromagnetic valves by a correction application voltage to which is added

  According to the above configuration, each solenoid valve is opened by a corrected applied voltage obtained by adding a correction value to the applied voltage, so that the amount of gas supplied by each gas supply means can be proportional to the applied voltage. The supply amount of the gas can be easily managed.

The typical sectional view showing the example of 1 composition of the low-pressure casting device of the present invention. Explanatory drawing of the correction method of an applied voltage. It is typical sectional drawing which shows the other aspect of each gas supply means of the low pressure casting apparatus of FIG. 1, FIG. 3A shows the low pressure casting apparatus provided with two 2nd gas supply paths, and FIG. 3B is 1st gas. 3C shows a low pressure casting apparatus using a gas cylinder having a common supply path and a second gas supply path, and FIG. 3C shows a low pressure casting apparatus using a gas cylinder having a common first gas supply path and two second gas supply paths. Indicates.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  As shown in FIG. 1, the low-pressure casting apparatus 1 of this embodiment is an apparatus used for low-pressure casting of a cylinder head of an internal combustion engine, for example, and is provided below the casting mold 2 and the casting mold 2. And a holding furnace 3 in which a molten metal M such as aluminum is heated and held.

  The casting mold 2 includes an upper mold 4 and a lower mold 5, and a cavity 6 having a shape along the outer shape of the cylinder head as a cast product is formed between the upper mold 4 and the lower mold 5. Here, the upper die 4 is mounted on a movable die base 7 and can be moved up and down by an actuator (not shown). The lower die 5 is fixed to a die base 8 that closes the upper opening of the holding furnace 3. .

  The lower mold 5 includes a gate 9 communicating with the cavity 6. The lower end of the gate 9 communicates with a stalk 10 that penetrates the die base 8 vertically and protrudes downward. The lower part of the stalk 10 is inserted into the molten metal M that is heated and held in the holding furnace 3. The stalk 10 acts as a guide means for guiding the molten metal M in the holding furnace 3 to the cavity 6.

  The holding furnace 3 includes a casing 11 made of a general steel material such as iron or steel (SS400 or the like), a furnace body 12 housed in the casing 11 and made of fireproof castable or the like, and the casing 11 and the furnace body 12. And a refractory layer 13 having a pore structure made of ceramic fiber or the like.

  First gas supply means 14 for pressurizing the molten metal M by supplying gas into the furnace main body 12 at a position on the peripheral wall surface of the holding furnace 3 and higher than the liquid level of the molten metal M in the furnace main body 12; A first pressure gauge 18 for detecting the pressure in the furnace body 12 is provided. As a gas for pressurizing the molten metal M, for example, compressed air can be used.

  The first gas supply means 14 has an air cylinder as the first gas supply source 15, one end connected to the first gas supply source 15, and the other end higher than the liquid level of the molten metal M in the furnace body 12. A first gas supply path 16 connected to the position and a first electromagnetic valve 17 that opens and closes the first gas supply path 16 are provided.

  In addition, the bottom of the peripheral wall portion of the holding furnace 3 is supplied with a second gas supply means 19 for filling the pore structure with air by supplying compressed air to the refractory layer 13 and a pressure in the refractory layer 13. A second pressure gauge 23 to be detected is provided.

  The second gas supply means 19 includes a second gas supply source 20 such as an air cylinder, and a second gas whose one end is connected to the second gas supply source 20 and the other end is connected to the bottom of the refractory layer 13. A supply path 21 and a second electromagnetic valve 22 that opens and closes the second gas supply path 21 are provided.

  The electromagnetic valves 17 and 22 and the pressure gauges 18 and 23 are all connected to the control device 24. The control device 24 controls the opening and closing of the electromagnetic valves 17 and 22 in accordance with the pressure detected by the pressure gauges 18 and 23. The control device 24 uses the correction application voltage obtained by adding a correction value to the application voltage operated by the operator so that the supply amount of the compressed air supplied from the gas supply paths 16 and 21 is proportional to the application voltage. The solenoid valves 17 and 22 are opened.

  Depending on the characteristics of the solenoid valves 17 and 22, for example, as shown by a solid curve in FIG. 2, the relationship between the applied voltage operated by the operator and the supply amount of compressed air is such that the applied voltage is small. When the valve 22 starts to open from the closed state, the change in the supply amount is small, and the change in the supply amount increases as the applied voltage increases. When the applied voltage further increases and the electromagnetic valves 17 and 22 are near full open, the supply is performed. Some changes in quantity are small.

  Therefore, the control device 24 opens the solenoid valves 17 and 22 with a corrected applied voltage obtained by adding a correction value to the applied voltage so that the output characteristic becomes a curve indicated by a broken line in the figure. As a result, the actual supply amount of compressed air with respect to the applied voltage becomes a straight line indicated by a two-dot chain line in the figure, and the actual supply amount of compressed air can be proportional to the applied voltage. Can be managed.

  Next, the casting method by the low pressure casting apparatus 1 of this embodiment is demonstrated.

  First, while the second electromagnetic valve 22 is opened by the control device 24 and the second pressure gauge 23 detects the atmospheric pressure state, the second gas supply means 19 causes the bottom of the refractory layer 13 to be detected. Supply compressed air.

  The compressed air supplied to the bottom of the refractory layer 13 diffuses in the lateral direction through the pore structure of the refractory layer 13, and is heated by the molten metal M in the furnace body 12 and diffuses upward. The entire layer 13 is filled in the empty structure. Then, the pressure in the space A (hereinafter referred to as a pressurized space) A higher than the liquid level of the molten metal M in the furnace body 12 and the pressure in the refractory layer 13 are made equal.

  Next, the control device 24 further opens the second electromagnetic valve 22 and supplies the compressed air to the refractory layer 13 by the second gas supply means 19 and opens the first electromagnetic valve 17. Compressed air is supplied to the pressurized space A by the first gas supply means 14.

  When compressed air is supplied to the pressurized space A by the first gas supply means 14 and the pressure in the pressurized space A increases, the liquid level of the molten metal M is pressurized, and the molten metal M rises in the stalk 10 and the gate It is press-fitted into the cavity 6 through 9.

  Subsequently, when both of the pressures detected by the pressure gauges 18 and 23 reach a predetermined pressure, the control device 24 closes the electromagnetic valves 17 and 22 to thereby apply pressure by the gas supply means 14 and 19. Maintain pressure. At this time, since the inside of the refractory layer 13 is filled with compressed air in the pore structure and maintained at the predetermined pressure equal to that in the pressurized space A, the furnace body 12 is cracked. However, the compressed air supplied from the first gas supply means 14 acts only to pressurize the molten metal M in the furnace body 12, and the pressurizing space A can be reliably maintained at the predetermined pressure.

  And the said cylinder head as a casting can be obtained by cooling and solidifying the molten metal M in the cavity 6 with the pressurization state by the compressed air in the pressurization space A maintained.

  After the molten metal M in the cavity 6 is solidified, the compressed air in the pressurized space A and the compressed air in the refractory layer 13 are discharged from a vent line (not shown) to release the pressure. The molten metal M is returned to the holding furnace 3 through the stalk 10. The cast product is taken out by moving the upper mold 4 upward and opening the casting mold 2.

  Next, another mode of the first gas supply unit 14 and the second gas supply unit 19 will be described with reference to FIG. FIG. 3 is a schematic diagram showing the holding furnace 3 and the gas supply means 14 and 19 in FIG. 1 in a simplified manner, and other configurations are omitted.

  As shown in FIG. 3A, the second gas supply means 19 may be one in which the downstream side of the second gas supply path 21 branches into two or more and connects to a plurality of locations at the bottom of the refractory layer 13. . By supplying compressed air to a plurality of locations of the refractory layer 13 by the second gas supply means 19 branched into two or more, the filling speed when filling the pore structure of the refractory layer is increased, The casting cycle time can be shortened, and further, the entire refractory layer 13 can be filled with compressed air without unevenness.

  As shown in FIG. 3B, the second gas supply means 19 is one in which the downstream side of the first gas supply path 16 branches into two as the second gas supply path 21. The first gas supply source 15 may also be used as the first gas supply means 14 as the second gas supply source. Thereby, since the apparatus can be constructed by one gas supply source 15, the cost can be reduced.

  Further, as shown in FIG. 3C, the second gas supply means 19 uses one of the two branches of the downstream side of the first gas supply path 16 as the second gas supply path 21, and further The downstream side of the two gas supply paths 21 may be branched into two or more and connected to a plurality of locations at the bottom of the refractory layer 13. Thereby, the filling speed when filling the pore structure of the refractory layer with the gas can be increased, the cycle time of casting can be shortened, and the entire refractory layer 13 can be filled with compressed air evenly. In addition to being able to do so, the apparatus can be constructed by one gas supply source 15, so that the cost can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Low pressure casting apparatus, 2 ... Mold for casting, 3 ... Holding furnace, 6 ... Cavity, 10 ... Guide means, 11 ... Casing, 12 ... Furnace main body, 13 ... Refractory layer, 14 ... First gas supply means, DESCRIPTION OF SYMBOLS 15,20 ... Gas supply source 16 ... 1st gas supply path, 17 ... 1st solenoid valve, 19 ... 2nd gas supply means, 21 ... 2nd gas supply path, 22 ... 2nd solenoid valve, 24 ... Control device, M ... Molten metal.

Claims (5)

A casting mold having a cavity having a shape that conforms to the outer shape of the cast product, a holding furnace provided under the casting mold for heating and holding the molten metal, and guiding the molten metal in the holding furnace to the cavity A low pressure casting apparatus that fills the cavity with the molten metal through the guiding means by introducing a gas into the holding furnace and pressurizing the liquid surface of the molten metal.
The holding furnace includes a metal casing, a furnace main body accommodated in the metal casing, and a refractory layer having a hole structure disposed between the metal casing and the furnace main body,
A low-pressure casting apparatus comprising: a first gas supply unit that supplies a gas that pressurizes the molten metal to the furnace body; and a second gas supply unit that supplies a gas to the refractory layer.   The low-pressure casting apparatus according to claim 1, comprising a plurality of the second gas supply means.   3. The low pressure casting apparatus according to claim 1 or 2, wherein the first gas supply means and the second gas supply means each include independent gas supply sources.   The low-pressure casting apparatus according to claim 1 or 2, wherein the gas supply source of the first gas supply means and the gas supply source of the second gas supply means include a common gas supply source. A low-pressure casting machine. In the low-pressure casting apparatus according to any one of claims 1 to 4,
The first gas supply means includes a first gas supply path that supplies gas to the furnace body, and a first electromagnetic valve that opens and closes the first gas supply path,
The second gas supply means includes a second gas supply path that supplies gas to the refractory layer, and a second electromagnetic valve that opens and closes the second gas supply path,
Furthermore, when the voltage applied to each solenoid valve is gradually increased to open each solenoid valve, the applied voltage is set so that the amount of gas supplied by each gas supply means is proportional to the applied voltage. A low-pressure casting apparatus comprising: a control device that controls the opening of each of the solenoid valves by a correction application voltage obtained by adding a correction value to the control valve.